ldap_authz_lib.js creates some useful users and roles that are required by later test execution. However, it can create these on a mongos. Mongos can only issue createUser and createRole to the Config Server ReplicaSet with wMajority. Because the test will want to probe all nodes of the CSRS, we actually want wAll. Because we cannot easily make mongos do what we want, and wMajority is fine for production deployments, we should await replication of our operations after invoking setupTest.